Conventionally, a device which is mounted to a machine driven by manpower such as a bicycle and calculates and displays information regarding driving of a bicycle, information regarding movement of a driver or the like is known. Such kind of device receives data from a sensor mounted to the bicycle and calculates, and displays predetermined information. The information to be displayed is force of the driver applied to a pedal (torque or the like).
Further, such kind of device displays the force applied to the pedal at a predetermined angular interval. Thus, it is necessary to detect an angle of a crank with respect to a reference position. For example, Patent Literature 1 discloses a device provided with a magnet group 21 in which a plurality of magnets is arranged on a circular-shaped frame-like member 20 fixed on a side surface of a frame of the bicycle at every 30° around a center C of the frame-like member 20, and a magnetic sensor 22 fixed on a chain ring and rotated together with the crank. In the device, the magnetic sensor 22 detects the angle by detecting each position of each magnet in the magnet group 21.
Further, Patent Literature 2 discloses a device which detects a rotation angle of a crank by using an angular velocity sensor 10, acceleration sensors 11, 12.